imageMap-methods {geneplotter} | R Documentation

## Write an HTML IMG tag together with a MAP image map.

### Description

Write an HTML IMG tag together with a MAP image map.

### Usage

      ## S4 method for signature 'matrix,connection,list,character'
    imageMap(object, con, tags, imgname)

### Arguments

`object` | Matrix with 4 columns, specifying the coordinates of the mouse-sensitive region . Each row specifies the corners of a rectangle within the image, in the following order: (left x, lower y, right x, upper y). Note that the point (x=0, y=0) is at the left upper side of the image.
`con` | Connection to which the image map is written.
`tags` | Named list whose elements are named character vectors. Names must correspond to node names in `object`. See details.
`imgname` | Character. Name of the image file (for example PNG file) that contains the plot.

### Details

The most important tags are `TITLE`, `HREF`, and `TARGET`. If the list `tags` contains an element with name `TITLE`, then this must be a named character vector containing the tooltips that are to be displayed when the mouse moves over a node. The names of the nodes are specified in the `names` attribute of the character vector and must match those of `object`.

Similarly, `HREF` may be used to specify hyperlinks that the browser can follow when the mouse clicks on a node, and `TARGET` to specify the target browser window.

Currently, only rectangular regions are implemented; the actual shape of the nodes as specified in `object` is ignored. Also, tags for edges of the graph are currently not supported.

This function is typically used with the following sequence of steps:

1. generate your graphic and save it as a bitmap file, e.g. using the `jpeg`, `png`, or `bitmap` device. At this stage, you also need to figure out the pixel coordinates of the interesting regions within your graphic. Since the mapping between device coordinates and pixel coordinates is not obvious, this may be a little tricky. See the examples below, and for a more complex example, see the source code of the function `plotPlate`.

2. open an HTML page for writing and write HTML header, e.g. using the `openHtmlPage` function.

3. Call the `imageMap` function.

4. Optionally, write further text into the HTML connection.

5. Close HTML file, e.g. using the `closeHtmlPage` function.

### Value

The function is called for its side effect, which is writing text into the connection `con`.

### Author(s)

Wolfgang Huber http://www.dkfz.de/abt0840/whuber

### See Also

`plotPlate`, `writeLines`

### Examples

    f1  = paste(tempfile(), ".html", sep="")
    f2  = paste(tempfile(), ".html", sep="")
    fpng = tempfile()

    if(capabilities()["png"]) {
      ## create the image
      colors = c("#E41A1C","#377EB8","#4DAF4A","#984EA3","#FF7F00","#FFFF33","#A65628","#F781BF","#999999")
      width  = 512
      height = 256
      png(fpng, width=width, height=height)
      par(mai=rep(0,4))
      plot(0,xlim=c(0,width-1),ylim=c(0,height-1),xaxs="i",yaxs="i",type="n",bty="n")
      cx=floor(runif(100)*(width-11))
      cy=floor(runif(100)*(height-11))
      coord=cbind(cx, cy, cx+10, cy+10)
      rect(coord[,1], height-coord[,2], coord[,3], height-coord[,4],
           col=sample(colors, 100, replace=TRUE))
      text(width/2, height-3, "Klick me!", adj=c(0.5, 1), font=2)
      dev.off()

      ## create the frame set
      cat("<html><head><title>Hello world</title></head>\n",
          "<frameset rows=\"280,*\" border=\"0\">\n",
          "<frame name=\"banner\" src=\"file://", f2, "\">\n",
          "<frame name=\"main\" scrolling=\"auto\">",
          "</frameset>", sep="",file=f1)

      ## create the image map
      href  =sample(c("www.bioconductor.org", "www.r-project.org"),nrow(coord),replace=TRUE)
      title =sample(as.character(packageDescription("geneplotter")),nrow(coord),replace=TRUE)
      con = file(f2, open="w")
      imageMap(coord, con,
        list(HREF=paste("http://", href, sep=""),
             TITLE=title, TARGET=rep("main", nrow(coord))), fpng)
      close(con)

      cat("Now have a look at file ", f1, " with your browser.\n", sep="")
    }

[Package geneplotter version 1.62.0 Index]